In the recent years, the personal computers (PC) and the networks have played essential roles in people's life, and now, we rely on computer networks to retrieve and share information. Today, individual computers can be connected to a power-line network, wherein the power-line network is constructed based on the electrical wires. Unfortunately, the magnitude of voltage in the electrical wires is much higher than the magnitude of voltage in signal itself; furthermore, the magnitude of noise in the electrical wires is also relatively high. However, the above problems can be solved by using the power-line adapter.
FIG. 1 is a diagram showing a power-line network, which is constructed by the electrical wires and power sockets in a house. Generally, there are a lot of power sockets in each division of a house, and these power sockets are connected in parallel by electrical wires. Today, these power sockets and electrical wires not only serve to supply the AC voltage (for example 120V 60 Hz), these power sockets and electrical wires can also be the components of the power-line network in the house. As depicted in FIG. 1, the AC voltage is supplied to the desktop computer 100 when the power plug 105 of the desktop computer 100 is plugged in the first power socket 110. Furthermore, the desktop computer 100 can be connected to the laptop computer 200 by using the electrical wires in the house if the network cable 115 of the desktop computer 100 is plugged in the first power line adapter 120 which is plugged in the second power socket 125, and also the network cable 215 of the laptop computer 200 is plugged in the second power line adapter 220 which is plugged in the third power socket 225.
FIG. 2 is a block diagram showing the circuit configuration of a conventional power line adapter. The power line adapter 300 comprises a power plug 302, a power line communication circuit 304, an Ethernet physical layer transceiver 316, a network socket 318, a bridge rectifier 320, a power transformer 322, and a DC/DC converter 324. The power line communication circuit 304 further comprises a coupling unit 306, a line driver 308, an analog front-end circuit 310, and a main controller 312.
In the conventional power line adapter 300, the power plug 302, the power line communication circuit 304, the Ethernet physical layer transceiver 316, and the network socket 318 together function as a data-transmitting module; the power plug 302, the bridge rectifier 320, the power transformer 322, and the DC/DC converter 324 together function as a power-transmitting module which is for providing the DC supply voltage (Vcc) needed by the operations of the power line communication circuit 304 and the Ethernet physical layer transceiver 316. That is, the AC voltage received by the power plug 302 is first converted to a first DC voltage by the bridge rectifier 320; the voltage level of the first DC voltage is further modulated by the power transformer 322; the modulated first DC voltage is further converted to the DC supply voltage (Vcc) by the DC/DC converter 324 and finally outputted to the power line communication circuit 304 and the Ethernet physical layer transceiver 316.
The network socket 318 is for the connection of the network cable (i.e., RJ45, not shown in FIG. 2) of a computer, and data can be derived to or derived from the computer through the Ethernet physical layer transceiver 316. In other words, when the computer is sending data out, the data outputted by the Ethernet physical layer transceiver 316 has to be processed and modulated by the main controller 312, the analog front-end circuit 310, the line driver 308, and the coupling unit 306, and then eventually transmitted to the electrical wires. Alternatively, when the computer is receiving data, the modulated data in the electrical wires is processed and demodulated by the coupling unit 306, the analog front-end circuit 310, and then eventually transmitted to the computer through the Ethernet physical layer transceiver 316.
Generally, the power line adapter is always plugged in the power socket, and accordingly the power is always consuming all the time even no cable connection is built or no data is transmitting between two computers. That is, 80%˜90% power, compared to the power consumed by the power line adapter operating in transmitting data, is waste. Therefore, designing a power line adapter capable of operated in a power-saving mode when no cable connection is built or no data is transmitting is the main purpose of the present invention.